Contribution of magnetic resonance imaging in the differential diagnosis of cardiac amyloidosis and symmetric hypertrophic cardiomyopathy.

BACKGROUND: Magnetic resonance imaging (MRI) provides a high-resolution study of atrial and ventricular myocardium depicting morphologic alterations in cardiomyopathies. Furthermore, in systemic amyloidosis, MRI demonstrates the capability to detect amyloid protein by tissue characterization. The aim of this study was to evaluate the potential of MRI in the diagnosis of cardiac amyloidosis.

METHODS: MRI was performed in 16 patients with cardiac amyloidosis and in 10 patients with symmetric hypertrophic cardiomyopathy. Myocardial ventricular and atrial thickness (septum, posterior, and lateral wall), right and left ventricular diastolic diameter, and atrial surface were compared. Ventricular myocardium signal intensity was then evaluated by sequences with an echo time (TE) of 20 and 60 ms as the expression of myocardial texture modification.

RESULTS: Significant morphologic differences between cardiac amyloidosis and hypertrophic cardiomyopathy were found in the right atrium surface (21.9 vs 17.2 cm2, respectively; P = .05), myocardial thickness of right atrial wall (9.3 vs 4.9 mm; P < .0001 ), and right ventricular free wall (10.6 vs 8.9 mm; P = .011 ). No significant differences were found in the interventricular septum (16.6 vs 17.8 mm), left ventricular posterior wall (18.2 vs 18.8 mm), and left atrial surface (17.4 vs 17.2 cm2). The signal intensity of cardiac amyloidosis was significantly lower with both TE 20 and TE 60 in comparison with hypertrophic cardiomyopathy and to a group of healthy volunteers.

CONCLUSIONS: MRI has a potential role in the noninvasive diagnosis of cardiac amyloidosis identifying typical morphologic markers and suggesting the presence of infiltrative disease by tissue characterization.